"A wonder-strike from the wonderboy of Australian football." The Australian TV commentary that heralded Tim Cahill's World Cup debut sounded overblown in 2006; he was a substitute when scoring an exquisite 89th-minute winner against Japan, after all. There is no disputing its prescience today. The talisman's mantle awaits Cahill in South Africa and, 13 years after arriving in England with only the promise of a trial at Millwall, it is a journey he is still struggling to comprehend.

Cahill, then 26, altered Australia's fortunes when Guus Hiddink introduced him against Japan. With one poacher's goal he became the first Australian to score at a World Cup finals, his second secured the country's first victory at a World Cup and he then created John Aloisi's luxurious third. The transformation did not cease there. Four years on Cahill's face adorns countless advertising campaigns back home, he had time for one brief weekend in Las Vegas this summer to wed his long-term partner, Rebekah Greenhill, before reporting for training in Sydney and there was promotional work to be done for the Tim Cahill Cancer Fund for Children. There was also the significant matter of finalising a new contract with Everton.

That was some impact substitution in Kaiserslautern.

"They knew who I was in Australia in 2006, but not to a great extent," the Everton midfielder admits. "Now, with the momentum of a second World Cup, it has gone crazy. I've been doing advertising campaigns with Kaká and Wayne Rooney, and other big players throughout the world, bringing out a DVD. It's been invigorating and I've enjoyed it, but there are so many things I've done that have been hard to take in. I remember cleaning boots at Millwall on £250 a week and feeling like a millionaire. I'd made it then. At that time, if I never played for another club it wouldn't have bothered me too much because I'd made it with a football team in England. I knew then that, no matter what happened, I would be able to tell my kids I made it with a professional club in England. That was probably one of the happiest times in my career."

There is a pressure on Australia at World Cup 2010 that was absent in Germany, where Hiddink's side – and a fanatical support – impressed before a controversial exit to Italy. Heightened expectation for South Africa has not been diluted by an ominous draw for the group stage and Saturday's 3–1 reverse to the USA would have caused more concern, although Cahill did manage to get on the scoresheet.

The midfielder, whose 20 goals in 40 international appearances explain his exalted status in Australia, accepts that demands have changed radically since 2006. "There is increased expectation on us this time, maybe among the fans but definitely among the media," he says. "It's such a hard group. Germany, Serbia and Ghana; they are all play-off matches and if you get through the group, anything is possible. That's the special thing about this World Cup. I don't think there is one big country that is nailed on to dominate in South Africa. I think there are going to be a hell of a lot of surprises all the way through. Anything can happen. People are saying we've got the hardest group, but what's the easiest? I don't think England have got an easy group. USA beat Spain for a start. Complacency and thinking you've got an easy group is really ignorant."

Unlike many prominent figures, Cahill can compete at this World Cup free of distraction about where he will be playing his club football next season. David Moyes's priority for Everton this summer is to keep intact the squad that finished last term with such conviction and Cahill was the first to commit with a new four-year contract. Not that anyone who witnessed Cahill's celebrations when Australia reached the knockout phase in 2006 had any doubt as to where his loyalties rested.

It was the night of Graham Poll's three card trick against Croatia and Australia had squeezed through. Thunderstruck by AC/DC reverberated around the Gottlieb-Daimler Stadium in Stuttgart and as Cahill cavorted around the running track he spotted a royal blue No17 jersey in the crowd. His next move was no insincere badge-kissing display of affection. He recalls: "I saw Everton jerseys at every Australia game in the last World Cup and when we qualified against Croatia there was one close to me, so I went into the crowd and swapped jerseys. It was a big moment in my life and something I'll never forget. It's priceless when I play for Australia and see an Everton shirt in the crowd, or when I play for Everton and there's an Aussie supporter there, and that was the most prized possession I have given away."

Jack Rodwell has since followed Cahill's lead in extending his Everton contract but doubts remain over several other key figures at the club, notably Steven Pienaar. The South African midfielder is approaching the final year of his deal at Goodison and has resisted the offer of a new deal that would give him parity with the highest earners in Moyes's squad. His anticipated departure is a distraction for Cahill. "Pienaar is a great player, a good character who is good for this team and we are good for him," he says. "I have to respect his decision because I am a professionaland I know that he is one of the biggest players for South Africa. Losing him would be a big loss but I think he needs to see what he would be losing if he left Everton. Hopefully we will sign him because it is a pleasure playing with him."